Enter Linux...

In 1991, a Finnish student decided that he needs a Unix-like system on his home PC, and started writing it, based on the Minix system.

He released the sources on the Internet, and was surprised to find many people sending him bug fixes and enhancements.

The system was generally a new kernel, together with a bunch of GNU utilities from the FSF (Free Software Foundation), and the XFree86 X window system implementation..

The system grew to what we know today. Like many Unices today, it attempts to support many standards (SVID, BSD4.3, XPG, POSIX).